James's Journal

In a maniacal scheme that is almost Bond-like in its level of unnecessary invention, he has updated his modus operandi and replaced the standard hydrocyanic acid with a "laser".

The trigger remains an unstable isotope, whose probability of decay within the time I'm in the box is 0.5, and so from his point of view, upon re-opening the box I will either be dead or alive, but until such time I will be both.

But what about me?

As the observer inside the box, I don't have to contend with quantum superpositions, though since the box itself is 100% effective at preventing the transfer of information, the outside world sits in one hell of a superposition itself. In fact, with my limited information, for all I can determine the Evil Doctor Schroedinger may himself be dead, until the box is opened.

But there are no superpositions within the box. I'm paying attention, and for the sake of argument, all available information within the box is reaching me at the appropriate speed of light.

Suddenly, an atom decays, or it doesn't. One of the two. For the time that it takes that information to reach me, there's a local superposition within the box. Assuming that I'm being reasonably well looked after, let's say that the isotope is three metres from my location. Light, moving at 300m m/s (okay, that's the speed in a vacuum, but we'll take it) will take ten nanoseconds to reach me, which is the maximum speed at which the information can travel. For those ten nanoseconds, there is a sphere around the particle, expanding at the speed of light, whose contents is indeterminate to anybody outside of that sphere.

So in the multiple universe interpretation of quantum mechanics, you're kind of being approached by this "decision wavefront", and when that hits you, you'll end up in one of the states that are indeterminate until that point. So the "live" state or the "die" state.

But see, Schroedinger has a "laser" in this system, and it's pretty responsive. So responsive, in fact, that the laser beam is sitting immediately behind the event horizon of the expanding multiple reality bubble. Also, the laser is powerful - assuming that ongoing consciousness requires a physical form to house it, then this laser will destroy consciousness on impact, because it's going to bloody zap the shit out of your physical form. Instant and permanent dematerialisation.

And this is the Quantum Suicide / Quantum Immortality thought experiment, in a slightly pedantic (but theoretically rigorous) form. The only information that can possibly reach you is the "you are alive" information. Conscious awareness of the alternative is impossible, because the laser moves at the speed of light, and will destroy your brain before your brain can know it's being destroyed.

In the event of any decision, your conscious awareness will only experience one of the available options. In this case, there is only one option available. From the point of view of the observer in the box, only one outcome is possible.

So while Evil Doctor Schroedinger will find you dead half the time, you'll never find yourself dead. From your point of view, this mechanism cannot kill you.

Except, here are the extensions to this...

Firstly, the laser must sit immediately behind the event horizon of the bubble. I mean, in theory, the laser should represent the event horizon. If you are able to perceive that you're going to die before you die, then you die. So, for example, if a little display on the "laser" lights up in the event that it's about to fire (which then happens a second later), and you see that, then you've already collapsed the possible realities - the multiple reality bubble has already hit you, and you've sadly ended up in the "you die" reality.

This is, of course, why you can't just jump off a cliff and expect quantum immortality to protect you. The blow that cracks your head open can still happen (and be perceived) before you die. And then you die. The whole point of this is that cessation of consciousness has to be simultaneous (or prior) to the receipt of information as to the outcome of the potentially lethal scenario.

Of course, if there's a light on the laser that warns you and collapses the potential outcomes into a single, certain outcome, then so long as you close your eyes (tightly enough to create a "Schroedinger Seal" - that is, an information barrier) you still have a chance there. Perhaps better than a chance - perhaps you're immortal in that scenario too. Worth thinking about.

So in theory, Quantum Immortality is only on offer if the mechanism for killing you is particularly well suited to the task - something that will kill you (literally) instantly, and at random.

The second extension questions whether there are always non-zero probabilities of survival in the instant of death. I mean okay, so I jump off the cliff, and my head is dashed open on the rocks below - damn. Does that truly give an absolute mortality rate of 100%? Or is there a risk (and it really is a nasty risk) that there is some terrible non-zero possibility that my consciousness could survive the incident? And continue to survive indefinitely no matter what the universe throws at me because nothing is 100% certain?

I'm not too worried about that - I'm not sure that there are always non-zero probability get-out scenarios in what would otherwise by the final instant of reality for your consciousness. Still, it's something to think about - could you get stuck, trapped by the quantum inevitability of your own consciousness? I mean, after my skull has been cracked open, I'm hardly going to be perceiving much of anything any more - does that mean that infinite possibilities open up in the absence of reality-collapsing perception? Will we all end up in our own nightmare universes as live brains in jars forever?

The third extension is actually rather a counterargument, which asks why consciousness need be continuous. This also covers the idea of an afterlife - if your mind can go on after death, then the whole "your consciousness will prevail regardless" logic breaks down into a crumpled heap. If continuity is not required, and consciousness is eternal through "reincarnation" but not present for every instant of the universe, then there is no need for consciousness to persist in a 50/50 live/die scenario. Not in the current body, anyway.